Sunn Solos 2 solid state

[bsco]

This amp had both speakers blew out....one was held together with tape the other had the surround rotted away and damaged cone.......the amp is fine....they had no labels...probably not original......Couldn't find a schematic or spec sheet on this particular one.....but everything else is there.... Quick question....what is the impedance of the original speakers?? They are wired in Parallel.....I have two 8 ohm speakers out of a Fender Frontman..that gives me 4 ohms total.......I am thinking they would do it.......am I correct???
Cheers....

[g1]

I think any SS amp worth it's salt should be able to go down to a 4 ohm load. But there are probably exceptions...

[g1]

To add: some came stock with two 128G speakers wired parallel. The 128G's are 8 ohm.
Here's a schematic if you need.

[52 Bill]

I remember fixing one of these a few years ago. It came in with low output. I went through the entire amp, strange design asymmetrical power supply. I think that the negative dc is something like 2/3 of the positive side.Spent a lot of time trying to find out why the negative supply was low. Eventually found a schematic for a similar Sunn amp and found out that the power supply was right.

Turned out to be a bad speaker, one was a dead short. So this amp will work with a low speaker load, well at least that one did.

And to answer Bernie's question, the original Sunn speakers were 8 ohms each in parallel for a 4 ohm load.

[bsco]

Ok guys...Thanks very much...I kind of figured it would....just wanted to double check..
Cheers,
Bernie

[bsco]

Got this beast back together....Have some hum there that varies when you move your hand over a certain area of the top of the cabinet...will have to shield it with some foil to see if that helps...also installed a good 3 prong power cord....this thing is loud when cranked.....especially with the overdrive on.....I'll have to pick up some adhesive backed foil tomorrow......and some staples.........
Cheers

[bsco]

one question..when you first power up and use the X20 switch, you get a loud thump in the speaker.After that initial switch use, it is fine....is this normal for this amp?? The switch as with most of the controls were noisy but a few sprays of contact cleaner fixed this up....outside of that, the amp works great.....
Cheers.........

[loudthud]

The thump is probably normal.

Here's a link to the schematics and board layouts: Sunn Solos II Schematic wanted

[teemuk]

The thump is normal. See, the switch works by either grounding the other end of R331/C328 or leaving it "floating". When the string is grounded the components are enabled, when "floating" they are disabled because current has no place to flow.

But the issue is this: When the switch is open and the other end of component string "floating" it lacks any steady DC reference. When you eventually provide one (e.g. zero volts) the current begins to flow, capacitors will charge to some voltage potential and you hear the quick period when voltages are "settling" as a "thump" through your speakers, pretty much the same thing as "thumping" when amplifiers get turned on or off.

A good design, however, doesn't leave "floating" nodes. Usual method to eliminate or at least minimize switch thump by great deal is to tie the "open" end of the component string to ground, but with series resistance that is so high in impedance that it effectively makes the branch look like it's "open" from signal's perspective.

Try, for example, connecting a 1-5 megaohm resistor in parallel with the switch: When closed the switch short circuits the resistor, when open the series resistance of the component branch is high, which for signal looks pretty much the same as open circuit. However, now you still have that branch of components steadily referenced to ground through that high-impedance resistor, no "floating", no DC level shifts, no "pops" or "thumps".

[bsco]

thanks for that tip teemug....much appreciated!!
Cheers

[Jazz P Bass]

Teemug??

[bsco]

Sorry... spelled it wrong.......teemuk.....

[Jazz P Bass]

I was thinking Tea Mug.

[nafo]

thanks for schematics!

[loudthud]

The link in post 8 above has moved to: https://forum.sunnstillshines.online...18693#msg18693